Problem: 9 erasers cost $7.74. Which equation would help determine the cost of 6 erasers?
Solution: There are several equations that could help determine the cost, each with a slightly different approach. If we let $x$ represent the cost of 6 erasers, we have the following proportion: $\dfrac{x}{6}$ We have to pay $7.74 for 9 erasers, and that can be written as a proportion: $\dfrac{\$7.74}{9}$ Since the price per eraser stays the same, these two proportions are equivalent. $\dfrac{x}{6} = \dfrac{\$7.74}{9}$